Research On Phase-shift Full-bridge ZVS DC/DC Converter With Capacitive Load

Nowadays, the medium-sized or large scale electric power energy storage iswidely applied in many fields, the energy storage technology of supercapacitorsplays an increasingly important role during a variety of energy storage techniquesdue to these features such as large power density, fast rate of charging anddischarging, high reliability, low maintenance cost as well as environmental friendlyand soon on.Then for the DC/DC converters applied to the supercapacitors that areregarded as capacitive load, are there generally some requirements like highersystem power capacity and safety isolation, what’s more, the full-bridge topology issuitable for middle or large power DC/DC converter, so this paper focuses onfull-bridge ZVS converter under the load of supercapacitor.As capacitive load mentioned for supercapacitor, this paper studies its basicprinciples and characteristics firstly, explores the voltage equalizing problembetween monomers of supercapacitor, then capacitive network load model isconstructed from multiple perspectives.This dissertation studies operating modes ofthe basic phase-shifted full-bridge ZVS converter and existing problems, then thepaper presents optimized design of full-bridge ZVS converter employing coupledinductor at primary side with detailed analysis of its working principle for therequirements on wider load range of achieving ZVS of all power switches and lessduty cycle loss, futhermore, in order to avoid the rectifiers’ parasitic oscillation ofthe secondary side, the active clamping circuit is adopted and analyzed.Related parameters of phase-shifted full-bridge ZVS converter mentioned inthis dissertation are designed, and then the small signal analysis model of full-bridgeZVS converter with capacitive load model chosen in the paper is derived by theapproach of average switching model, corresponding closed-loop compensationregulators according to charging strategies of supercapacitor are deduced,and theimplementation methods in digital control system are provided. Based on thedetermined parameters of capacitive load model, this dissertation carries outperformance comparative analysis of basic and optimized full-bridge ZVS converterthrough simulation of PSIM software including DSP digital control system, and thenrelated hardware circuits have been set up, experimental tests are implemented by aprototype considering the charging control strategies of supercapacitor, and theexperimental results validate the feasibility and superior performance of theconverter’s theory analysis and design in the thesis.